Frequency modulation



June 26, 1945. TU I K 2,379,325

FREQQEN CY MODULA'I ION Qriginal' Filed Aug. 29, 1941 AMPL Ml/Z UPI/ER L /M/ T E A INVENTOR HfiiZZ/N/CK BY .A'IITORNEY Patented June 26, 1945 UNITED STATES PATENT orrlcs FREQUENCY MODULATION Harry Tunick, Rye, N. Y., assignor to Radio Corporation of America, a corporation of Delaaware Original application August 29,

1941, Serial No. 7

408,738, now Patent No. 2,282,103, dated May 5, i 1942. Divided and this application January 21,, 1942, Serial No. 427,572

10 Claims. (Cl.

parent as the more detailed description thereof proceeds.

In the accompanying drawing, the single figure is a wiring diagram of a frequency modulation transmitter employing my present invention. 1 In the transmitting system illustrated in the drawing, the oscillator tube 900 may have either crystal 992 connected between the plate 904 and grid 906 or, as shown, the series tuned circuit 998. Thelatter is connected, by means of switch 919, between the plate 904 and'grid 906. The screen grid 92B is supplied with voltage through radio frequency choke 922 by-passed by condenser 924. The plate 904 is supplied with' plus voltage through choke 930 by-passed by by-passing condenser 992. Transformers 934 and 93S insert alternating signal voltages in the plate and screen voltage leads. These signal voltages are derived from potentiometer 940 connected to the secondary of transformer 942 whose primary is connected across the plates of pushpull amplifier 944 energized from audio or signaling amplifier 996.

Since like voltage changes applied to the screen 929 and plate 904 produce opposite effects on the frequency of oscillation of tube 900, transformers 939 and 934 are so poled as to oppositely swing the screen 920 and plate 904 in voltage in accordance with signal voltages derived from amplifier 946. The output circuit 950 of the oscillator-909 is fed tothe limiter 952 which may be a power amplifier and/or frequency multiplier. The latter, represented by rectangle 952, is connected to and energizes the transmitting antenna 954.

Having. thus described my invention, what I claim is: y

l. A system for producing frequency modulated waves comprising an electron discharge device oscillation generator, said generator including a vacuum tube having a plate, a screen grid, a control. grid and a cathode, a source of 179-1715) modulating voltages and circuits for applying said modulating voltages oppositelyto said screen grid and plate whereby the frequency of oscillations generated is varied in accordance with said modulating voltages.

2. In a frequency varying system, an oscillation generator having an anode, a cathode, a control grid and a screen grid, circuits interconnecting said electrodes whereby oscillations of substantially constant frequency are regeneratively generated, a source of modulating voltages, and means for applying said modulating voltages oppositely to the anode and screen grid whereby said oscillations are varied in frequency in accordance with said modulating voltages.

3. Apparatus as claimed in claim 1, characterized by the fact that the mean frequency of oscillations generated is controlled by a piezoelectric crystal.

4. A system for producing frequency modulated waves comprising an electron discharge device oscillation generator, said generator including a vacuum tube having a plate, a screen grid, a control grid and a cathode, a source of modulating voltages and circuits for applying said modulating voltages oppositely to said screen grid and plate whereby the frequency of oscillations generated is varied in accordance with said modulating voltages, a limiter for limiting the frequency modulated waves to waves of substantially constant amplitude, and a transmitting circuit for transmitting the limited waves.

5. A system for producing frequency modulated waves comprising an electron discharge device oscillation generator, said generator including a vacuum tube having a plate, a screen grid, a control grid and a cathode, a source of modulating voltages and circuits for applying said modulating voltages oppositely to said screen grid and plate whereby the frequency of oscillations generated is varied in accordance with said modulating voltages, a frequency multiplier for frequency multiplying thefrequency modulated waves, and a transmitting circuit for transmitting the frequency multiplied frequency modulated waves.

6. In a frequency varying system, an, oscillation generator having an anode, a cathode, a control grid and a screen" grid, circuits interconnecting said electrodes whereby oscillations of substantially constant frequency are regeneratively generated, a source of modulating voltages, and means-for applying said modulating voltages oppositely to the anode and screen grid whereby said oscillations are varied in frequency in accordance with said modulating voltages, means for frequency multiplying and limiting the frequency modulated waves, and a transmitting circuit for transmitting the frequency multiplied and limited waves.

7. Apparatus for producingfrequency modulated waves comprising an electron discharge device having plate, screen grid, control grid and cathode electrodes, a piezo-electric crystal connected to a pair of said electrodes, a high frequency output circuit connected to another pair of said electrodes, a source of modulating voltages and circuits for applying said modulating voltages oppositely to said screen grid and plate whereby the frequency-of oscillations, normally controlled by said crystal, are varied in frequency in accordance with said modulating voltages.

8. Apparatus for producing frequency modulated waves comprising an electron discharge device having plate, screen'grid, control grid and cathode electrodes, a piezo-electric crystal connected to a pair of said electrodes, a high frequency output circuit connected to another pair of said electrodes, a source of modulating voltages and circuits for applying said modulating voltagesoppositely to said screen grid and plate whereby the frequency of oscillations, normally controlled by said crystal, are varied in frequency in accordance with said modulating voltages, a

limiter for limiting the frequency modulated waves so produced to waves of substantially constant amplitude, and a transmitting circuit for transmitting the limited waves.-

9. Apparatus for producing frequency modulated waves comprising an electron discharge device having plate, screen grid, control grid and cathode electrodes, a piezo-electric crystal connected to a pair of said electrodes, a high frequency output circuit connected to another pair of said electrodes, a source of modulating volt ages and circuits for applying said modulating voltages oppositely to said screen grid and plate whereby the frequency of oscillations. normally controlled by said crystal, are varied in frequency in accordance with said modulating voltages, a frequency multiplier for frequency multiplying the frequency modulated waves so produced, and

a transmitting circuit connected to said frequency multiplier for transmitting the frequency multiplied frequency modulated waves.

10. In a frequency varying system, an oscillation generator having an anode, acathode, a control grid and a screen grid, circuits including a piezo-electric crystal inter-connecting said electrodes whereby oscillations of substantially constant frequency are regeneratively generated, a source of modulating voltages, and means for applying said modulating voltages oppositely to the anode and screengrid whereby said oscillations are varied in frequency in accordance with said modulating voltages, means for frequency multiplying and-limiting the frequency modulated waves, and a transmitting circuit for transmitting the frequency multiplied and limited waves.

HARRY TU NICK. 

